In the field of oncology, cancer treatment is often performed using radio frequency (RF) ablation techniques. Conventional ablation techniques use an array of RF needles or tines (sometimes referred to as a “tine array”), which may be configured to deploy in a pre-determined shape or pattern for transferring RF energy into surrounding tissue. The needles or tines act as electrodes which are electrically connected to a RF generator. The needles or tines thus transmit RF energy into the surrounding tissue for the thermal coagulation and/or necrosis of tissue. For example, in an undeployed state, tines are positioned at a target area while housed within the lumen of a cannula. The undeployed tine array enclosed within the cannula may be positioned by inserting the cannula through bone and tissue into a target area. Once inserted, the electrode tine array may be deployed by forcing the electrode tines out of a cannula and into the surrounding target tissue. After deployment, RF energy may be transmitted from the electrode tine array to ablate the target tissue, causing heating and eventual necrosis of cancerous or malignant tissue. RF ablation occurs when a high frequency alternating current flows from one electrode to another, completing a current path, causing ionic agitation. Ionic agitation occurs around an active electrode as a result of frictional heating in the tissue surrounding the electrode tines (e.g., electrodes, RF needle probes, and the like) on an array, leading to cell death and necrosis. After ablating the target tissue, the electrode tine array is then retracted into the cannula and the cannula is removed from the target area.
RF ablation probes may be configured in either monopolar or bipolar mode. In monopolar mode, one electrode (e.g., negative) is located within or on a cannula. In order to complete the circuit for RF energy, a separate electrode pad or the like is typically placed on the skin of the patient. Other bipolar-based devices use multiple electrodes or electrode arrays on a single device. For example, the CONCERTO™ needle electrode device (Boston Scientific Scimed, Inc., Maple Grove, Minn.) uses two electrically independent opposing arrays that are contained within an insulated cannula. RF energy passes between the two arrays and heats the tissue surrounding and in between the arrays.
The electrode array may be deployed via a distal end of the cannula. In other configurations, however, the electrode array may emerge from an inner lumen of the cannula via a plurality of holes or passageways located around the periphery of the cannula. With this last configuration, however, the holes or passageways located within the cannula can reduce the structural integrity of the cannula. This is particularly important because the columnar strength of the cannula is important as the device may require considerable pushing force to insert the cannula into the tissue to reach the desired target zone.
There thus is a need for a RF ablation device that is able to deploy an array of electrodes via side-located slots or apertures which at the same time provides the device with high columnar strength. In addition, the device would permit minimal spacing between the tips of the electrodes within the array such that the RF ablation device can efficiently ablate the target tissue.